Alcoholic and non-alcoholic liver fibrosis remains an unsolved challenge for the hepatologist as it can lead to cirrhosis and end-stage liver disease, a life-threatening condition that necessitates liver transplantation. Current therapeutic strategies for the treatment of liver fibrosis include changes in diet, life-style and/or medications to allevate the underlying cause of disease. Since liver disease is typically diagnosed following significant scar formation, adjuvant strategies that oppose the molecular and cellular program of fibrosis that drives liver disease and activate matrix degrading pathways are urgently required. A preponderance of preclinical data in models of fibrotic liver disease speaks to collagen catabolizing activity of endogenous peptide hormone Relaxin (H2R). Translation of these findings into clinical regimen has been painfully slow in large part due to the costs and logistica difficulties associated with commercial production of recombinant human (rh) H2R. Using molecular modeling-and medicinal chemistry-based drug design, Angion Biomedica has developed a library of single chain, short length H2R-like peptides that can be chemically synthesized and potentially offer multiple clinico-commercial advantages over rhH2R therapy. SBIR Phase I studies have identified a lead antifibrotic candidate, ANG-4011, from within this library, that has excellent drug-like properties and is therapeutic in multiple preclinical models f renal and hepatic fibrosis, opposing matrix deposition in kidney and liver. In partnership with the internationally recognized laboratory of Prof. Kathryn Uhrich (Rutgers University, NJ), and representing a landmark step in sustained in vivo delivery of peptides, we have developed a clinically compatible, biodegradable, microsphere-based extended release formulation for ANG-4011. The proposed milestone-driven SBIR Phase II study is designed to make a comprehensive evaluation of our lead candidate in preclinical models of liver fibrosis while optimizing its delivery. Data from this SBIR Phase II program will allow for entry of this lead candidate to the preclinical safety/toxicology battery to be completed under the aegis of the SBIR Phase IIb competing renewal mechanism. The ultimate objective of this program is to bring an H2R-like antifibrotic to clinical trials for treatment of liver fibrosis.